If you want to use Starlight (which very likely would be the overall by far best model for your needs but also needs A LOT of time/patience) and are on a budget the 5070 with 12 GB is about the minimum for the GPU. If you can spend the extra bucks, go for the 5070TI/16GB.
The CPU doesn’t really matter much for Starlight, so a middle-class one is sufficient here. AMD/Intel does not really matter that much, either - so take the one you can get the cheapest combo with the 5070.
Edit: since you’re going for used hw the 4070(TI) would be a viable option as well. But in any case the gfx card should have at least 12GB VRAM.
And P.S.: RAM latency really only comes into account when using the older „traditional“ models at high resolutions, e.g. upscaling 1080p to 4k.
That money definitely is better spent on a better GPU.
I am back and have got my build completed - took the advice and I have:
AMD Ryzen 9 9950X3D 4.3 GHz 16-Core Processor
ASUS TUF Gaming GeForce RTX™ 5070 Ti 16GB GDDR7 OC Edition
I’m ready to get started - have been reading through some threads - am I correct in thinking I should be loading my video and using the “Starlight” function rather than using the Presets (FHD) and default AI model (Proteus)?